HOW MUCH DO YOU KNOW???

TEST YOUR KNOWLEDGE ON EYES

All answers found in the blog since inception.

      1.       An eye specialist that performs surgery on the            eye is called an  __________________________.

2.       Close to _______________per cent of cataract surgeries successfully result in better vision.

3.       An eye specialist that fills the prescription for a pair of glasses is called an_______________________.

4.       An astigmatic cornea is shaped like a football/soccer ball

5.       Myopia is an eye condition in which you have trouble seeing clearly in the ______________distance.

6.       A  plus/minus lens is used in the correction of hyperopia.

7.       T/F (True or False)  The function of fusion is necessary to see in 3D.

8.       What is the meaning of visual acuity of 20/20?

9.       T/F Being able to see 20/20, is having perfect vision.

10.   Name the leading cause of blindness in North America.

11.   A person unable to see in 3D, does not have any ____________perception.

12.   What is the Snellen Chart used for?

13.   What is visual acuity the measurement of?

14.   The second most common cause of permanent vision loss is called ______________________.

15.   The sclera is part of the ___________________tunic.

16.   The ________________is transparent and covers the iris, pupil and anterior chamber.

17.    A procedure used to help the elderly with sagging skin on the upper eyelids which may interfere with vision is called ____________________________.  This is more commonly performed as a cosmetic procedure.

18.   T/F  Presbyopia commonly occurs around the age of 40

19.   The external retina is made up of two cell layers.  Name them.

20.   A method used to fit frames cosmetically is called the theory of ______________________.

21.   Ultraviolet radiation measuring a wavelength of less than __________________nm is the most biologically harmful.

GLAUCOMA

GLAUCOMA

This condition is the second most common cause of permanent vision loss.

 
Glaucoma is a disease in which there is optic nerve damage which cannot be reversed. The optic nerve is responsible for the function of carrying visual impulses from the nerve to the brain.  The majority of the cases experience visual loss due to an increased pressure in the eye, called intraocular pressure or IOP.

There are 4 types of  Glaucoma:

• Open-angle (chronic) glaucoma
• Angle-closure (acute) glaucoma
• Congenital glaucoma
• Secondary glaucoma

The clear fluid which fills the anterior part of the eye is called aqueous humor.  This liquid is produced by the iris and exits the eye through an area called the anterior chamber angle or just the angle.  Anything that slows or blocks the flow of this fluid out of the eye will cause pressure to build up in the eye. This pressure is called intraocular pressure (IOP).  In most cases of glaucoma, this pressure is high and causes damage to the optic nerve.

Open-angle (chronic) glaucoma is the most common type of glaucoma.

 RISK

Certain factors can make it more likely that a person may develop Glaucoma.  Those risks include:

 

• Having family history of glaucoma damage
• having optic nerve or visual field findings on the border between glaucoma and normal
•  African-American ethnic background
• Being myopic (near-sighted)
• Having a thin cornea
• Being at higher risk of developing high IOP due to a condition in which pigment is dispersed  

If glaucoma is caught when the signs are very early and treatment begun at that time, the risk of developing serious visual loss is quite small.

OPEN ANGLE GLAUCOMA:      

This is the most common type and constitutes about 90per cent of all cases.  The patient experiences no real symptoms but the IOP

becomes elevated until visual loss occurs.  This happens in both eyes or the condition is bilateral.  This is caused by the degeneration or rigidity of trabecular meshwork, Schlemm’s canal and venous channels.  Although the production of aqueous is constant, the outflow decreases so IOP goes up. The treatment for this condition is usually prescribed drops or surgery. 

The drops help to reduce production of aqueous and increase drainage through outflow channels.  Drops commonly prescribed are called Diamox which is a miotic drug.

ANGLE CLOSURE GLAUCOMA:

 This condition results in a sudden increase in IOP due to blockage of anterior chamber angle.  Unlike Open Angle Glaucoma, this type has very pronounced and deliberate symptoms.  All outflow of aqueous ceases or stops.  This immediately increase the IOP which causes pain and visual loss.  This usually develops in patients with a narrow (shallow) anterior angle.  There is a sudden onset of symptoms which include a swollen, edematous cornea, reddening of the eye, nausea and vomiting.  The treatment includes dehydrating the eye and using a miotic drug which pulls the iris away from canal of Schlemm.  Surgery is also an option.

 

 

CATARACT

 Condition:  Cataract

 

 

This is a naturally occurring condition which happens as one ages.  In this condition, the lens, located behind the iris and pupil, becomes opacified or appears cloudy due to the dead cells gathering in the lens.

This common condition results in vision loss for patients over 40 years of age.   World-wide, cataracts is one of the leading causes of vision loss.  Others include Macular Degeneration, glaucoma and diabetic retinopathy.  Statistics show that approximately 244,000 cataract operations were performed in Canada in 2001 (National Coalition for Vision Health, 2005).

 

Other Causes

Other causes of cataract which may result in an earlier age may be due to prolonged and excessive ultraviolet light exposure, diabetes, smoking and use of certain medications.  These medications generally include steroids, statins and phenothiazines. 

 

Cataract Surgery

 

Surgery is the only way to remove cataracts in order to restore vision. Cataract surgery is routinely performed and is commonplace in the United States and Canada.  The success rate of this surgery is quite high. Close to 95 percent of cataract surgeries successfully result in better vision.  Cataract surgery involves the removal of the opacified lens replaced with an artificial lens called in intraocular lens or IOL. 

 

Procedure

 

With advances in medicine, the modern cataract procedure is called Phacoemulsification.  This involves using a high frequency ultrasound probe which obliterates the cloudy lens into tiny fragments which are then taken out from the eye with suction.

 As with other surgeries, cataract surgery also has a risk of complications.  This risk is increased if there is a pre-existing eye disease or other medical condition.  However, complications are usually dealt with successfully. 

Recently, a new way to remove cataract has emerged which uses a Femtosecond laser, which is similar to the LASIK procedure.  This new method, approved by the FDA, is even more reliable in terms of accuracy and safe. 

Recovery

The procedure is quite quick and lasts approximately 15 minutes.  Medicated eye drops are prescribed to be used for a period of a few weeks after surgery.  A protective shield must be worn while sleeping for about 7-10 days after surgery.  Post-operative sunglasses are to be worn for protection from the sun and other light sources during eye recovery.

Types of Cataracts

• A subcapsular cataract is located at the back of the lens. Those most likely to get this type of cataract are diabetics or those taking high doses of steroid medications.
• A nuclear cataract as the name suggests, this type of cataract forms deep in nucleus of the lens. Nuclear cataracts are usually associated with aging.
• A cortical cataract occurs in the central nucleus of the lens.  Wedge shaped opacities appear in the periphery of the lens and move towards the center.

 

LOW VISION

WHAT DOES LOW VISION MEAN?

Low vision is not ‘bad vision.’  It is simply vision that cannot be corrected with visual aids to achieve 20/20 visual acuity.  There only exists the means to enhance or provide low vision aids to improve the quality of life for those going through vision loss.

It is a visual impairment that cannot be corrected by standard glasses, contact lenses, medicine or surgery.  Having low vision interferes with a person’s ability to perform everyday activities.  It has an impact on lifestyle and thus a low vision aid patient requires aids to help enhance the amount of vision they do have.

STATISTICS

·        1 out of 20 people in America has low vision

·        1 in eight Americans is 65 years of age or older

·        By 2030, number of people 65 years and older is expected to double

(Lighthouse National Survey on Vision Loss 1995)

·        More than 22 billion dollars is spent annually on care and services for people who are blind or visually impaired

    EARLY SIGNS:

Often times, depression and low self-esteem set in when a person is first diagnosed with vision loss.  Other emotions such as anger, fear, and grief are also experienced and are entirely normal.  Often, people’s reactions to vision loss are similar to those experienced in bereavement; initially, there is often a period of denial, when the person experiencing visual loss is in shock and believes their state is not permanent.   Things that were previously routine, such as performing household chores, taking care of children, reading the newspaper, or going to the corner store, may all become very challenging tasks.  Cooking, exercising, and socializing may even seem impossible.

COPING WITH VISION LOSS

 Vision loss requires a person to cope with an increased amount of stress while being able to function in an environment with fewer stimuli.  Relationships with loved ones often become strained.  Without proper assistance, people who experience the disintegration of important relationships may end up living in fear and may become homebound. This is particularly true of seniors.

Those suffering from vision loss require rehabilitation to restore the skills they need to perform everyday activities, to restore their quality of life, and to bring about a sense of normalcy.  Of great concern to many who suffer vision loss, is the idea of losing their independence.  Depending on the degree of vision loss, a caregiver or someone to help out may be required in the interim or on a permanent basis.  A move to a short or long-term care facility is an alternative.

 

Vision loss is incredibly difficult to fathom and accept. Those in denial are at risk of increased difficulties, as their recovery from vision loss is undermined by their lack of motivation to rehabilitate. The most important step for anyone in this situation is to seek support.  Things are incredibly difficult for those who are alone and need help.  Dealing with the resultant emotions alone can be as burdensome as dealing with the vision loss

CHILDREN

Low vision aids is the solution to visual loss.  Vision loss is not restricted only to the ageing population.  In fact, a child’s visual requirements are just as important if not, more important than that of adults.  Certain conditions, if caught early enough may be preventable and treatable.  According to research, approximately 25% of school age children have some sort of visual problem and six out of ten children have difficulty reading due to a visual problem that is either uncorrected or undetected.

Vision screening in pediatrics is important in the early detection of a condition known as Amblyopia or ‘lazy eye.’ Amblyopia is a functional defect most commonly caused by strabismus or unequal refractive error.  This condition is the leading cause of unilateral vision loss in people between the ages of 20-70.  If caught in the early stages, treatment can begin which can increase the child’s chance of improving their vision.  If the condition remains untreated, or is treated for best possible vision, the child may still be able to improve the quality of their vision with low vision aids.

     CAUSES: 

-Macular Degeneration, Cataract, Problem with optic nerve (Glaucoma, Diabetic Retinopathy)

          -inherited disorder of receptor cells—Retinitis Pigmentossa

 VISUAL ASSESSMENT:

          Optometrist or Ophthalmologist will test the patients for low vision correction.    They must determine what type of field defect:

• Macular Degeneration:  Central Field Defect—peripheral still intact 
•  A condition called Diabetic Retinopathy is on the rise with children and elderly—several scotomas spread around
• Glaucoma:  Peripheral Field Defect—you want minification to shrink the text into the center of good vision
•            Retinitis Pigmentossa:  All over defect

.           Once you determine where the visual field defect is, then you know how to help the patient via low vision aid.  i.e. if the blind spot is in the center, use a magnifier to get it out of the area of the scotoma.    i.e. if the blind spot is in the periphery, use a minifier—to shrink things so that they fall into the center

 HIGHER RISK FOR LOW VISION
                ·        people 65 years of age or older (age related Macular Degeneration)

·        African American and Hispanics over the age of 45

·        genetically higher risk for developing diabetes and diabetic retinopathy

·        African American higher risk of developing Glaucoma

 

 

CONTACT LENSES

 

There are Nearly 75 million contact lens wearers in the world. 

About half of them live in the United States.

If contact lenses are to replace glasses, then they need to be extremely comfortable as well as provide excellent vision with little or no adverse effects.  Otherwise, what would be the point?  Patient criteria must be met in order to have an ideal contact lens candidate.   Generally, the following considerations are taken into account when determining if someone is a good candidate for contact lenses.

            1.  Eyelids:   

                     - If lids are tight, they may cause rotational force on lens

                     - If lids are retracted, this may cause lid impact
                     - If the patient is experiencing Ptosis (drooping of the eyelid):
                       drooping lid may not move the lens sufficiently                                        
          2.  Blinking patterns:

                     -tear film must be good and general health of the eye and

                      cornea.  If the eyes are too dry, then wearing contact lenses
                      May become difficult unless you start to administer eye drops
                      frequently.

3.  Safety is very important in fitting contact lenses.  There are many occupations which will rule out the wearing of contact lenses such as:

           Welders, miners, construction workers, jobs that involve
            sandblasting  or drilling

4.  Infection--the cornea may be infected due to the environment emitting: radiation, dust, vapors, for fumes.  Profession such as plumbers, auto mechanics, furniture builder--cannot get their hands perfectly clean—this can contaminate lenses

5.  There is a saying in the opticianry profession --PATIENT SELECTION:  AVOID THE 5 D’S

           The dirty, drunk, diseased, disabled and the dumb

 GENERAL GUIDELINES FOR FITTING CONTACT LENSES

For Rigid Gas Permeable (RGP) lenses—usually fit either on K, flatter than K or steeper than K (Keratometry readings—we will get into this later)

For Soft lenses—ideally fit to obtain the three-point touch.  For the three-point touch, the contact lens must come in contact with the corneal apex and the periphery on both sides of the cornea.

Soft contact lenses are usually fit larger than the corneal diameter for centration and stability.  A well-fit contact lens should show:  good centration, adequate movement, stable vision, clear undistorted keratometry mires.

A contact lens fit may be too loose or too tight—may change the lens parameters for a better fit i.e.  change the diameter or radius of contact lens
(If you increase diameter, lens will be tighter)
(If you decrease radius, lens will be tighter)

ASTIGMATIC EYES

For Astigmatic eyes, they require special toric lenses. 

If an astigmatic eye is fit with normal soft lenses, the patient will experience fluctuating or blurred vision

WEARING SCHEDULE FOR SOFT

If new to wearing soft lenses, you must have a ‘break-in’ period in which your eyes need to adjust to the contact lens.  The first day of wear, it is recommended to keep them on for 4 hours.  The wearing time may be increased by 2 hours daily until all-day wearing schedule is achieved.  The patient should return to the office for follow-up in 1 week, then 2-week intervals for three visits.   During these visits, lenses should be evaluated and lens changes made if needed.

--keratometer:  follow-up keratometry—pay attention to mires and to changes to radius of curvature

COMPLIANCE

Deposit formation on lens surface is affected by:

          -lens material
          -the wearing time
          -lens care system used

A build up of protein, lipids, and minerals on the lens may result in the following:

       -decreased vision, red and irritated eye, a change in the fit of the lens, a decrease in oxygen transmission of the lens.  Studies have shown that surface deposits extend over 50% of a hydrogel lens within 5 minutes after the lens is worn and over 90% of the lens after 8 hours.

The protein build up on the lens may cause GPC (Giant Papillary Conjunctivitis)—corneal and bulbar conjunctival inflammation.  Methods of Cleaning:  Surfactant cleaners, Oxidative Agents, Enzyme cleaners, Ultrasound, disinfection

 

DISPOSABLE CONTACT LENSES

Disposable contact lenses are a good choice for the sake of health.  As they are being replaced daily, there is less chance of protein and bacteria build up.

A patient will save on lens cleaners and solutions as well since, contact lenses are discarded after use

 

ASTIGMATISM



ASTIGMATIC EYE

What is it?

 This is an error with the way light is focused on the retina.  Similar to nearsightedness or farsightedness, astigmatism is a refractive error.  In a normal eye, light rays come to a single point focus on the retina.   In an astigmatic eye, however, light rays do not come to a single point focus and thus a clear image is not produced.  There are many focus points in an astigmatic eye—some in front or behind the retina, or both.

The cornea of an eye is normally shaped like a ball, or sphere.  However, this need not always be the case.  An astigmatic eye is shaped like a football with one meridian being more curved than the one 90 degrees away from it.   To understand meridians, think of the directional North South East West cross sign.  The North-South is the 90 degree meridian and the East West is the 180 degree meridian. 

The meridians are measured in terms of their ‘steepness.’  One meridian is usually flatter than the other.

Astigmatism may also be caused by the shape of the lens within the eye.  This is referred to as lenticular astigmatism as opposed to corneal astigmatism. 

SYMPTOMS OF ASTIGMATISM

Vision appears to be blurry and distorted at various distances for a person experiencing uncorrected astigmatism.   Generally, after a period of time, a person may experience eye strain, headaches and will often find the need to be squinting.  Astigmatism may be classified as regular and irregular.

REGULAR ASTIGMATISM

Regular astigmatism can be broken down into five categories:

1.) SIMPLE MYOPIC ASTIGMATISM

 -One meridian is emmetropic—light rays focus on the retina(no correction is required—Rx Plano)

Example:  Plano -2.00 x 090

-Opposite meridian is myopic—light rays come to a point focus in front of the retina.  A minus lens is required for correction

2.) COMPOUND MYOPIC ASTIGMATISM

-Light rays in both meridians fall short of the retina

Example:  -1.00 -2.00 x 090

The first number (-1.00) is the sphere power (in diopters) for the correction of myopia in the flatter (less nearsighted) principal meridian of the eye.

          The second number (-2.00) is the cylinder power for the additional  myopia       correction in the more curved principal meridian.

The third number (90) is called the axis of astigmatism. This is the location (in degrees) of the flatter principal meridian, on a 180-degree rotary scale (in which 90 degrees designates the vertical meridian of the eye, and 180 degrees designates the horizontal meridian).

3.) SIMPLE HYPEROPIC ASTIGMATISM

-One meridian is emmetropic (light rays focus on the retina)

                     -One meridian is hyperopic (light rays focus behind the retina and a plus                lens is required for correction)
                     Example:  Plano +2.00 x 090

4.)  COMPOUND HYPEROPIC ASTIGMATISM 

-Both meridians are hyperopic

-Light rays in both meridians focus behind the retina.

Example:  +1.00+2.00 x 090

     5.)  MIXED COMPOUND ASTIGMATISM

                   -One meridian is farsighted and the other is       nearsighted

  IRREGULAR ASTIGMATISM

Irregular astigmatism results when the principal meridians are not 90 degrees apart.  This ends up happening as a result of an eye injury which may scar the cornea.  Eye surgery and a condition called Keratoconus (cone shaped cornea as a result of thinning) as well results in the principal meridians not being perpendicular to one another. 

Astigmatism is corrected by using contact lenses, glasses or by having refractive surgery.

 

 

THEORY OF COSMESIS

 

Did you know that there is an actual theory as to how to pick a pair of glasses that will suit your face shape?

It is called the theory of Cosmesis and it is essentially a method used to fit frames cosmetically. The goal, in accordance with this theory is to achieve the best possible appearance with the frames chosen taking into account the following considerations:

     1.)     classification of frames

 2.)     facial shape

 3.)     facial features

 4.)     color (skin tone)

 5.)     hair style

Frame selection is often a process of trial and error.  An optician can assist in choosing a frame, but a frame consultant or salesperson can offer helpful suggestions as well. 

CLASSIFICATION OF FRAMES BY WEIGHT

You will notice that frames can be physically heavy or light depending on the material used to make them and as well on the style of the frame.

Usually a heavy frame is recommended for people with large, broad features.  A medium frame is recommended for people with normal features or with large features and small stature.  A light frame is recommended for small delicate features, usually women with childlike features or for children.

 

CLASSIFICATION OF FRAMES BY COLOR

Eyeglass frames come in a variety of colors which can help to make a fashion statement or help to draw attention away from a problem area or towards an area of the face you may be trying to enhance. 

The following are frame colors that are available in an optical store.

1.)       Solid color—even color throughout

2.)       Vertically gradient—brow bar darker, lower eyewire light or clear

3.)       Horizontally gradient- darker temporally, lighter at bridge

4.)       Clear bridge (area at top of nose)

5.)       Multicolor

6.)       Yellow gold

7.)       White gold

FACIAL SHAPE

A Frame can influence the shape of a face either by its lines being similar to and accenting those of the face, or by its lines being dissimilar to and de-emphasizing those of the face.

i.e. a round frame shape de-emphasizes the squareness of a face or a square frame shape ( a frame having straight lines) de-emphasizes roundness in a face.

 THE WELL-PROPORTIONED FACE

 Being human means that we are all made uniquely and therefore we may not all have the ‘perfect well-proportioned’ face.  But we need not worry as this is where the Theory of Cosmesis can help with giving the illusion of having a well proportioned face.  Regardless of the shape of your face, the key in selecting a good frame is to keep the frame in proportion to your face.

  A face consists of 3 sections:  In a well-proportioned face, all sections are equal

1.)   top of the head to top of the eyes

2.)   eyes to bottom of nose

3.)   bottom of nose to chin

An individual with the following face shapes should choose the recommended frame styles to give them the best possible appearance.

      i.  Heart Shaped—The frame should cover the width of the      face.  Frames with       detail towards the temples draws attention away from the slimmer lower part       thus deemphasizing sharp features or problem areas.


 

     ii.     Square Shaped—Rectangular or oval shaped frames are well suited to a square face.  To deemphasize the ‘squareness,’ avoid picking frames with sharp corners or frames that are flat at the bottom.  Round frames generally are a good pick.
 

 iii.  Round Shaped—To deemphasize the ‘roundness,’ a good choice of frame would be one that’s rectangular or a narrow oval.  The frame should sit high on the face to give the illusion of more length from below the frame to the bottom of the chin.

 iv.  Oblong Shaped—Frames well suited to this face shape are those with a strong horizontal line or frames that are rounder.  A frame with detail at the bottom will draw attention away from the length of the face thus minimizing the length.   

 

v.     Oval Shaped—This is the IDEAL face shape in that an individual may wear most any shaped frame and they will be able to carry it off well.